It is known that a scouring, dyeing or finishing operation for a textile material, for example, yarn or fabric, can be carried out by using an organic solvent, for example, trichloroethylene, perchloroethylene, 1,1,2-trifluoro-1,2,2-trichloroethane or 1,1,1-trichloroethane, as a medium for a scouring agent, dye, or finishing agent. Also, it is known, in the case of trichloroethylene, perchloroethylene or 1,1,2-trifluoro-1,2,2-trichloroethane, after completing the above-mentioned operation, the residual portion of the organic solvent in the textile material can be recovered by introducing the textile material into a bath containing hot water at a temperature high enough to cause evaporation of the organic solvent, so as to allow the residual organic solvent to be released from the textile material and to be vaporized together with water in the bath. The recovery can be carried out by cooling the vapor mixture of the organic solvent and water generated from the hot water bath, so as to condense it, and then, by separating the condensed organic solvent from the condensed water. The above-mentioned methods are disclosed, for example, in Japanese Patent Application Publication (Kokoku) Nos. 45-1656 and 50-3431, and British Pat. Nos. 773,968 and 825,402.
However, the above-mentioned recovering method has never been applied to 1,1,1-trichloroethane. This is because it has been believed that it is impossible to recover 1,1,1-trichloroethane from a textile material without deterioration in quality of the textile material, when the textile material containing 1,1,1-trichloroethane is brought into contact with hot water. It is known that the contact of 1,1,1-trichloroethane with hot water results in hydrolysis of 1,1,1-trichloroethane at a high hydrolysis rate, which corresponds to about 40 times that of perchloroethylene and about 60 times that of trichloroethylene. The hydrolysis of 1,1,1-trichloroethane results in undesirable formation of hydrochloric acid and acetic acid, which will cause the quality of the textile material to be deteriorated and the vessel of the hot water bath to be corroded.
Also, it has been believed that the hydrolysis causes the yield of the recovered 1,1,1-trichloroethane to be poor. Moreover, it has been believed that the hydrochloric acid and acetic acid which are generated by the hydrolysis of 1,1,1-trichloroethane, are distributed not only in the hot water bath and the water vapor generated from the hot water bath, but also, in the vapor of 1,1,1-trichloroethane released from the textile material. Carrying this concept to its logical conclusion, it has been believed that the hydrochloric acid and acetic acid distributed in the 1,1,1-trichloroethane cause the recovered 1,1,1-trichloroethane to be poor in quality.
Furthermore, it has been believed that, when 1,1,1-trichloroethane is used as a solvent for treating the textile material, the deterioration in quality of the textile material can be prevented only by using a mixture of 1,1,1-trichloroethane with a stabilizer consisting of, for example, at least one member selected from dioxane, methyl butynol and nitromethane, which stabilizer is effective for preventing the hydrolysis of 1,1,1-trichloroethane. However, the stabilizer per se is expensive and it is difficult to recover the stabilizer together with 1,1,1-trichloroethane, because the stabilizer is water-soluble. Therefore, the use of the stabilizer results in an undesirable high cost of the treatment of the textile material with 1,1,1-trichloroethane-containing treating agent.
However, the inventors of the present invention discovered the fact that the deterioration of the textile material and the corrosion of the vessel of the hot water bath can be prevented by maintaining the pH of the hot water bath at a level of 4.0 or more. This discovery causes the treatment of the textile material with the 1,1,1-trichloroethane-containing treating agent without using the stabilizer to be possible. Also, it was discovered by the inventors that the generated hydrochloric acid and acetic acid are mainly distributed in the hot water bath, and therefore, substantially no hydrochloric acid and acetic acid are contained in the recovered 1,1,1-trichloroethane. Accordingly, the recovered 1,1,1-trichloroethane exhibits a good quality.